Conventional cold-mixed asphalt mixtures can achieve mixing construction at normal temperature to some extent so as to reduce the consumption of energy. However, cold-mixed asphalt mixtures have poor pavement performance, which fail to satisfy the requirements of modern road surfaces on asphalt materials and can be only used for low-quality road surface pavements or small-range repairing.
A waterborne polyurethane emulsion refers to a polyurethane which uses water as a dispersion medium and is free of or contains little amount of organic solvent in the system, and inherits excellent properties of solvent-type polyurethanes such as good low-temperature resistance, good abrasion resistance, high adhesion, etc., while it has the advantages of no pollution, good safety and reliability, good compatibility, easiness of modification, etc. It has gradually substituted solvent-type polyurethanes and is widely used in coatings, adhesives, fabric coatings and finishing agents, leather finishing agents, paper surface treating agents, fiber surface treating agents, etc. As an emulsified asphalt modifier, it has good physical and chemical properties and can significantly improve the pavement performance of emulsified asphalt.
Patent CN201110188772.9 discloses a waterborne polyurethane epoxy resin modified emulsified asphalt, which is formed by forming a polyurethane epoxy resin by a reaction with epoxy chloropropane or an epoxy resin after the chain extension of isocyanate with a polyol, forming a waterborne polyurethane epoxy resin by the association with a polyether polyol emulsifier, an auxiliary and water, modifying an emulsified asphalt, and curing with a modified fatty amine epoxy resin curing agent. It has a complicated process of synthesis and a lot of influential factors, and is difficult to ensure the uniformity; and meanwhile, the content of waterborne polyurethane is too low, which insufficiently contributes to the strength, and the application performance of this material is not evaluated in this patent.
An acrylate monomer has a carbon-carbon unsaturated double bond and forms an acrylate resin through a polymerization reaction. Acrylate resin does not only have very high photostability, thermal stability, and chemical stability, but also has the advantages of excellent weather resistance, corrosion resistance, chemical resistance, stain resistance, high adhesion, etc. Also, it has the features of abundant sources of raw materials and relatively low cost. In the wider sense, a waterborne acrylic resin comprises a waterborne acrylic resin emulsion, a waterborne acrylic resin dispersion in water, and an waterborne acrylic resin solution in water. They possess important applications in building coatings, but have not been used in roads yet.
As an asphalt modifier, the waterborne acrylic resin emulsion has good physical and chemical properties, and may improve the resistance of asphalt to corrosion by acids, alkalis, and organic solvents, improve high-temperature and low-temperature properties of asphalt, reduce the sensitivity of asphalt to temperature, increase the elasticity of asphalt, reduce aging tendency of asphalt, improve the adhesion of asphalt to stone materials, and improve the fatigue resistance of asphalt, so as to overall improve the pavement performance of emulsified asphalt. In recent years, there have been related studies in China, for example, Chinese Patent Application No. 201410023492.6 discloses a preparation method of an acrylic resin emulsified asphalt, which is studied mainly aiming at the technical problems that emulsified asphalt has long drying time and poor water resistant properties, and is mainly a water-resistant emulsified asphalt material. Chinese Patent Application No. 201410023481.8 discloses a preparation method of a urea resin emulsified asphalt, which has long reaction time and complex operation required for the synthesis of the urea resin emulsified asphalt.
After years' normal operation of a highway, rut and cracks will occur on part of the road surface. Although the function of the road surface is not influenced transitorily, utilization properties of the road surface will be reduced and the useful life will be shortened, if treatment is not timely performed.
Micro-surfacing is the highest form of an emulsified asphalt slurry overlay, which is a preventive curing technical measure developed on the basis of slurry seals, and is suitable for the preventive curing of important traffic roads, such as highways, city main roads, airport runways, etc. Micro-surfacing may improve slip resistance, repair slight surface unevenness and rut, prevent infiltration of water, and prevent aging and loosening of the road surface, so as to significantly improve utilization properties of the road surface and effectively elongate the useful life of the road surface; as a preventive maintenance technology, micro-surfacing may also be directly used for a surface wearing course of a newly built road so as to reduce the use of expensive stone materials, to decrease construction cost, and to significantly reduce the occurrence of early water damage; and furthermore, micro-surfacing further has the advantages of good convenience for construction, low construction cost, short time to open traffic, etc., and has a very wide prospect for application.
Micro-surfacing is a thin layer structure, wherein a polymer modified emulsified asphalt, a mineral aggregate, water, and an additive are mixed in a certain weight ratio and paved on a road surface by specialized equipment and the traffic is opened rapidly. It has high requirements for constituent materials: firstly, the aggregate used must be firm, wear resistant, and clean, and type II or type III gradation is typically used as the gradation of the stone material; and secondly, in order to ensure a better adhesion between the asphalt and the stone material, a cationic emulsified asphalt is typically used, and polymer modification is needed, and SBR latex or SBS is typically used for modification, so as to ensure that a micro-surfacing overlay may still achieve a relatively long useful life even under the action of heavy traffic.
As an emulsified asphalt modifier, the waterborne epoxy resin itself has good physical and chemical properties and can significantly improve the pavement performance of emulsified asphalt. However, pH is required to be adjusted to about 2-3 in the preparation process of a cationic emulsified asphalt, while the addition of a waterborne epoxy resin emulsion containing an amine-type curing agent will disrupt the equilibrium system of the cationic emulsified asphalt, leading to the failure of the effect of emulsification, and has a significant phenomenon of caking.
Current studies in the art are mainly focusing on the modified emulsified asphalt material itself, while studies on waterborne polymer modified emulsified asphalt mixtures have not been prevalent yet. The emulsified asphalt mixture said herein refers to a mixture containing emulsified asphalt used in engineering, particularly road engineering, which may be, for example, used for asphalt concrete pavement materials, asphalt road surface repair materials, slurry seals for curing, micro-surfacing, asphalt mortar for high-speed railways, etc.
However, in the field of road engineering, there remains a need for developing a waterborne polymer modified emulsified asphalt mixture having a simple preparation method and good properties.